IBM DBCA-204860 Hard Drive Specifications - Page 19

Single Track Seek Time, Full Stroke Seek, Average Latency

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The seek time is measured from the start of motion of the actuator to the start of a reliable read or write operation. Reliable read or write implies that error correction/recovery is not employed to correct for arrival problems. The Average Seek Time is measured as the weighted average of all possible seek combinations. Weighted Average = max SUM (max + 1 n) (Tn.in + Tn.out) n=1 (max + 1) (max) Where: max = Maximum Seek Length n = Seek Length ( 1 to max ) Tn.in = Inward measured seek time for a n track seek Tn.out = Outward measured seek time for a n track seek 3.3.3 Single Track Seek Time Function READ Write Figure 7. Single Track Seek Time Typical 2.5 msec 3.0 msec Max 4.0 msec 4.5 msec The single track seek time includes settling time but does not include command overhead. Single track seek is measured as the average of one (1) single track seek from every track in both directions (inward and outward). 3.3.4 Full Stroke Seek Function Read Write Figure 8. Full Stroke Seek Time Typical 23.0 msec 24.0 msec Full stroke seek is measured as the average of 1000 full stroke seeks. 3.3.5 Average Latency Max 30.0 msec 31.0 msec RPM 4200 Figure 9. Latency Time Time for a revolution 14.3 msec Average Latency 7.1 msec Drive Characteristics 11

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The seek time is measured from the start of motion of the actuator to the start of
a reliable read or write
operation
.
Reliable read or write implies that error correction/recovery is not employed to correct for arrival
problems.
The Average Seek Time is measured as the weighted average of all possible seek combinations.
max
SUM (max + 1
n) (Tn.in + Tn.out)
n=1
Weighted Average =
(max + 1) (max)
Where:
max
= Maximum Seek Length
n
= Seek Length ( 1 to max )
Tn.in
= Inward measured seek time for a n track seek
Tn.out = Outward measured seek time for a n track seek
3.3.3
Single Track Seek Time
Figure 7. Single Track Seek Time
The single track seek time includes settling time but does not include command overhead.
Single track seek is measured as the average of one (1) single track seek from every track in both directions
(inward and outward).
3.3.4
Full Stroke Seek
Figure 8. Full Stroke Seek Time
Full stroke seek is measured as the average of 1000 full stroke seeks.
3.3.5
Average Latency
Figure 9. Latency Time
Function
Typical
Max
READ
2.5 msec
4.0 msec
Write
3.0 msec
4.5 msec
Function
Typical
Max
Read
23.0 msec
30.0 msec
Write
24.0 msec
31.0 msec
RPM
Time for a revolution
Average Latency
4200
14.3 msec
7.1 msec
Drive Characteristics
11